Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h,w = map(int, input().split())
G = [['#']*(w+2)]
white = 0
for i in range(h):
    G.append(['#']+list(input()) + ['#'])
    white += G[i+1].count('.')
G.append(['#']*(w+2))

G[1][1] = 1
que = deque([[1,1]])
while que:
    y,x = que.popleft()
    d = G[y][x]
    for dy,dx in ((1,0),(-1,0),(0,1),(0,-1)):
        ny = y+dy
        nx = x+dx
        if G[ny][nx] == '.':
            G[ny][nx] = d+1
            que.append((ny,nx))
if G[h][w] == '.':
    print('-1')
else:
    ans = white - G[h][w]
    print(ans)